**1. Introduction**

In Morocco, with an area of 49731 ha and an annual production of 809762 t [1], apple cultivation is exposed to the pressure of various harmful biological agents; approximately 182 synthetic pesticides are registered against these organisms [2]. Aphids are small, soft-bodied insects with long, slender mouthparts used to pierce stems, leaves and other tender parts of plants and, suck up sap from the host plant. They are among the most dangerous pests of crops; they directly weaken plants by sucking their sap; these results in curling and deformation of the leaves of young shoots, which affects the photosynthetic function of the attacked plant. Among the indirect damage, aphids are vectors of many phytopathogenic viruses and the secretion of honeydew favoring the development of sooty mold on leaves and

fruits [3, 4]. The green apple aphid, *Aphis pomi* De Geer (Hemiptera, Aphididae) is 1.3–2.3 mm long and light green or yellowish green in color, with short antennae and black or dark brown siphunculi; asexual development goes through 4 Nymphs and an adult (**Figure 1**). It is a monoecious holocyclic species, i.e., the aphid has one sexual generation and several asexual (parthenogenetic) wingless and /or winged generations; they grow on the same plant species or on plants of related species. The aphid is widely distributed in the northern hemisphere [5]. This species is very harmful to pome fruit (Rosaceae), especially apple trees; its infestations are rife regularly. The species is particularly harmful in nurseries and young orchards. To control aphids, apple growers only use synthetic insecticides; thus, 82 pesticides are registered against aphids [2]; these pesticides are broad spectrum and effective against many pests other than aphids; they mainly belong to the groups of organophosphates, carbamates, pyrethroids and neonicotinoids. However, the intensive use of these products raises health, environmental and ecotoxicological problems (e.g., [6–8]). The use of these pesticides also generates resistance phenomena in pests [9–11]. In addition, they can cause the resurgence of secondary pests [12]. This latter phenomenon is characterized by a reversal of the biological response such as the shortening of the duration of the development, the increase in fecundity with fertility and longevity due to the application of the sublethal doses of the pesticides used [13]. Besides the unwise use of pesticides increases the mortality of natural enemies that contribute to pest control [14, 15]; which increases the cost of production and affects the efficiency of the techniques applied and the environmental sustainability of the agroecosystem [16].

To mitigate the ecotoxicological, environmental and social consequences of synthetic pesticides; the research for effective, economical, safe and ecological alternative methods compatible with sustainable development is therefore imperative. In other words, adopt the concept of integrated pest management (IPM) [17, 18]. Among the products likely to replace synthetic pesticides and, at the same time reduce pollution of natural ecosystems; valorization of OMW in plant protection responds well to this dilemma.

Around the world, there are more than 800 million productive olive trees, occupying an area of 10 million hectares; olives are used either as table olives or for the production of olive oil. Global table olive production was 2900000 tons,

*Valorization of Olive Mill Wastewater in the Control of* Aphis pomi *De Geer 1773… DOI: http://dx.doi.org/10.5772/intechopen.100016*

while olive oil production exceeded 3300000 tons [19]. The Mediterranean region alone provides 97% of the total world olive oil production, being close to 3 million tons [20]. The oil extraction is carried out by three processes, namely the traditional process (press process), the two-phase process and the three-phase process [21]. However, olive oil production is also accompanied by the generation of huge amounts of by-products and waste that leave a cluttered environmental footprint [22]. Indeed, during the extraction of oil by press or three-phase systems, enormous quantities of vegetable water are produced annually, the reported volumes are estimated at around 440 L of OMW for 100 kg of processed olives [23], i.e., from 10 to 30 million m3 per year [24]. These effluents are acidic and very rich in organic compounds including polyphenols [24–26]. The management of OMW is generally unregulated; they can be discharged directly into terrestrial and aquatic ecosystems without prior treatment. This results in disastrous environmental consequences due to their high polluting capacity (e.g., [27–30]). Thus, non-target organisms in these natural compartments are negatively affected (e.g., [31–35]). In addition, the presence of organic and inorganic pollutants makes this waste flow toxic for bacteria and other microorganisms used in biological treatments [32]. In Morocco, where olive tree occupies an area of 1073493 ha and produces 1912238 t of olives [1], oil extraction is carried out mainly by traditional press and, in few cases by the threephase or two-phase system; thus, it generates enormous quantities of OMW. Like other countries, the dumping of vegetable waters is also disposed mainly on soils and in rivers. Indeed, as indicated in **Figure 2**, during the extraction of oils from the olives, the OMW are evacuated in a channel (**Figure 2A**) discharging them either in a watercourse (**Figure 2B** and **D**) either in a terrestrial environment (**Figure 2C**).

#### **Figure 2.**

*Olive mill wastewater (OMW) disposed into ecosystems ((A) discharge channel, (C) soil receptacle, (B and D) Oued receptacle).*

With regard to the harmful effects of OMW and to avoid or mitigate the issues associated with them, the scientific community has felt the need to promote them in several areas. This is because vegetable waters contain valuable components, such as water, organic compounds and a wide range of nutrients that could be recycled. Then, OMW could be recycled and used as a feedstock to generate cost effective compounds such as antioxidants, enzymes, biogas, soil conditioners, feeds, foods, fertilizer, etc. (e.g., [36–42]).

In crop pest management, OMW have been tested against weeds, fungi and nematodes [43], olive psyllid [44], green apple aphid [45], date palm white worm [46], tomato broomrape [47], plant pathogens [48], Mediterranean fruit fly fruits [49]. For full details, bibliographic reviews provide a synthetic overview on the use of OMW in plant protection [50, 51]. For our part, after having evaluated the toxicity of OMW with respect to *Gammarus gauthieri* (Amphipoda, Crustaceae) [31] and earthworms [33], we tried to valorize crude OMW in the control of pests by testing them against *A. pomi*. This work aimed at replacing synthetic pesticides used in aphid control and, at the same time reducing pollution of natural ecosystems owing to OMW. To this end, the valorization of OMW in plant protection responds well to this dilemma. In this chapter, the results relating to the efficacy of crude olive mill wastewater with respect to the green apple aphid are presented, as well as their physicochemical composition.
